JPH11170086A - Water soluble flux - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain water soluble flux compatible with a human body and a environment, not having corrosiveness and excellent in wettability and solder spread by containing a rosin soap in water. SOLUTION: A rosin soap is produced by dissolving alkali into water, heating and adding rosin while agitating. In the case water soluble flux is a liquid type, the rosin soap of 1-30 pts.wt. is dissolved in 100 pts.wt. water, in the case of a paste type, the rosin soap of 31-60 pts.wt. is dissolved, further a organic solvent is preferably not contained. Solder spread is improved by adding an organic acid, a halide and an organic halide. By adding a fungus preventive of 0.001-0.1 wt.% in a water soluble flux, long term storage is made possible. The fungus preventive preferably uses water soluble. An adding agent of surface active agent, thickner, defoaming agent, etc., may be added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous flux, and more particularly, to an aqueous flux having good wettability.

[0002]

2. Description of the Related Art In recent years,
In the electronic industry and the like, miniaturization of products and speeding up of electronic circuits are regarded as important. However, miniaturization of products and speeding up of electronic circuits have conflicting aspects in product reliability, and it is not easy to satisfy both requirements simultaneously. In particular, the miniaturization of the product makes it difficult to solder the circuit board and the electronic components. When the contacts between the electronic circuits become complicated, whether or not the soldering is defective causes a short circuit and a bonding failure. Of course, it is not possible to solder a complicated circuit by an operation conventionally performed one by one with a soldering iron. Therefore, as a method of soldering an electronic component to a circuit board, a method of treating the board surface (copper) with a flux for removing an oxide film on the board surface (copper) and then immersing the board surface (copper) in a molten solder bath has been used. I have.

Such a flux has an effect of removing an oxide film of a metal to be joined, preventing reoxidation of the metal surface, and lowering the surface tension of the molten solder. Also,
The flux must be non-corrosive and have excellent wettability. As a flux that satisfies the above-mentioned requirements, for example, Japanese Patent Application Laid-Open No. H3-113293 discloses a flux containing solder particles whose surface is coated with rosin. Also, Japanese Patent Application Laid-Open No. 57-16519
No. 8 discloses a soldering flux obtained by adding rosin amine hydrohalide to rosin or a derivative thereof. However, since rosin is essentially insoluble in water, the flux disclosed in the above publication contains an organic solvent such as alcohol and acetone. Therefore, such a flux has problems such as adversely affecting the human body and the environment. It is believed that these serious problems can be solved by changing the medium in the flux from an organic solvent to water. However, as described above, since rosin is insoluble in water, it is necessary to make the rosin contained in the flux water-soluble. Accordingly, an object of the present invention is to provide an aqueous flux which is friendly to the human body and the environment, has no corrosiveness, has excellent wettability, and has an excellent solder spread rate.

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that water contains rosin soap produced by reacting all or a part of resin acid, which is a main component of rosin, with alkali. Has obtained the finding that the above object can be achieved. The present invention has been made based on the above findings, and provides an aqueous flux containing rosin soap.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the aqueous flux of the present invention will be described in detail. The aqueous flux of the present invention contains rosin soap. As the rosin soap, it is preferable to use an alkali soap that is soluble in water generated by reacting all or a part of the resin acid constituting the main component of rosin with an alkali. The method for producing the rosin soap is not particularly limited, and it can be produced by a conventionally known method. For example, it can be produced by dissolving an alkali in water, heating, and adding rosin while stirring.
As the rosin, any rosin can be used, and examples thereof include maleic acid-modified rosin, maleic acid-modified rosin ester, hydrogenated rosin, disproportionated rosin, polymerized rosin, gum rosin, wood rosin, and tall oil rosin. . Examples of the alkali include inorganic amines such as ammonia and morpholine; aliphatic primary amines such as ethylamine; aliphatic secondary amines such as dimethylamine; aliphatic tertiary amines such as trimethylamine; Unsaturated amines; alicyclic amines such as cyclopropylamine; and organic amines such as aromatic amines such as aniline. Further, the amine is preferably a low-boiling amine, specifically, a compound having a boiling point of 200 ° C. or lower. The heating temperature is preferably from room temperature to a temperature higher by 10 ° C. than the melting point of rosin, and more preferably from 30 ° C. to the melting point temperature of rosin. When the aqueous flux is produced as a solution-type aqueous flux, the amount of the rosin used is 10% water.
The amount is preferably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, based on 0 parts by weight. When the aqueous flux is produced as a paste-type aqueous flux, the amount is preferably 31 to 60 parts by weight, more preferably 40 to 50 parts by weight, based on 100 parts by weight of water. The amount of the alkali used varies depending on the acid value of the rosin, but is preferably about the equivalent of the acid value to about three times the equivalent of the acid value.

[0006] The aqueous flux of the present invention contains the rosin soap produced as described above. When the aqueous flux is of a solution type, the content of the rosin is preferably 1 to 30% by weight, more preferably 5 to 20% by weight in the aqueous flux. Further, when the aqueous flux is a paste type, 31 to 31 in the aqueous flux
It is preferably 60% by weight, more preferably 40% by weight.
５０50% by weight. Further, in the aqueous flux of the present invention, the remainder of the rosin soap is water, therefore,
In the aqueous flux of the present invention, the content of water is preferably 70 to 99% by weight when the aqueous flux is a solution type.
And more preferably 80 to 95 weight. Also,
When the aqueous flux is of a paste type, the water content is preferably 40 to 69% by weight, more preferably 5 to 69% by weight.
0 to 60% by weight. In the present invention, it is preferable that rosin soap is dissolved in water, and particularly preferable is one containing no organic solvent. The aqueous flux of the present invention may contain a small amount of an organic solvent, in which case the content is preferably less than 30% by weight in the aqueous flux.

[0007] The aqueous flux of the present invention may contain an organic acid, a halide or a halogenated organic acid salt. The spreadability of the solder can be improved by adding such an organic acid, halide or halogenated organic acid salt. As the organic acid, for example,
Glutaric acid and adipic acid are mentioned, and the halide is, for example, hydrochloric acid and ammonium chloride, and the halogenated organic acid salt is, for example, methylamine chloride. Further, a fungicide or the like can be added to the aqueous flux of the present invention. By adding the fungicide in this way, the aqueous flux of the present invention can be stored for a long period of time. As the antifungal agent, a conventionally known antifungal agent can be used without any limitation, and it is preferable to use a water-soluble antifungal agent. For example, 2-n-octyl-4-isothiazoline-
3-one or the like can be used. When the above-mentioned antifungal agent is contained in the aqueous flux of the present invention, the content is preferably 0.001 to 0.1% by weight, more preferably 0.005 to 0.05% by weight in the aqueous flux. It is. Further, various additives may be added to the aqueous flux of the present invention as needed. Examples of the additive include a surfactant, a thickener, and an antifoaming agent.
When the above additives are added, the amount of the additives is preferably 0.05 to 5% by weight based on the total weight of the aqueous flux.

[0008]

[Evaluation criteria for aqueous flux]

(1) Evaluation of Wettability of Flux A predetermined amount of the obtained aqueous flux was dropped on a steel sheet that had been subjected to an acid value treatment using a Komagome pipette, and the wettability to the steel sheet was visually observed and evaluated according to the following evaluation criteria. Table 2 shows the evaluation results. A: The aqueous flux spreads instantaneously. ：: The aqueous flux gradually spreads. X: The aqueous flux does not spread while maintaining a spherical shape.

(2) Evaluation of spreadability of solder The evaluation was performed according to JIS-Z-3197-1986. That is, put the solder ring and flux on the oxidized steel sheet,
It was melted at a temperature of 250 ° C. for about 30 seconds to spread the solder. Measure the height of the solder and measure the spread rate according to JIS-Z-3197.
−1986. (3) Evaluation of Corrosion Conducted according to JIS-Z-3197-1986. That is, the obtained aqueous flux was placed on a steel sheet from which an oxide film had been removed using an abrasive paper in an organic solvent, heated and melted at a temperature of 250 ° C. for about 5 seconds, and then cooled at room temperature. The three test pieces were left for 96 hours in a constant temperature bath at a temperature of 40 ± 2 ° C. and a relative humidity of 90 to 95%, and compared with a comparative test piece stored at room temperature to observe the presence or absence of corrosion. (4) Appearance of aqueous flux The appearance was evaluated with the naked eye according to the following evaluation criteria. Table 2 shows the evaluation results. Uniform: There is no sedimentation or suspended matter, and it is uniformly dispersed or solubilized. Separation:
There was sedimentation or suspension and separated into two or more phases.

Examples 2 to 6 and Comparative Examples 1 and 2 Example 1 was repeated except that the reaction was carried out using the compositions shown in Table 1.
The same operation as described above was performed to obtain an aqueous flux. In addition, in Example 4, gum rosin powder was added and dispersed before use, and in Comparative Example 1, heating was not performed. The obtained aqueous flux was evaluated in the same manner as in Example 1. Table 2 shows the evaluation results.

[0011]

[Table 1] Example Comparative Example 1 2 3 4 5 6 1 2 Hydrogenated rosin 10 2 10 Polymerized rosin 5 10 Gum rosin 5 5 28% ammonia water 3.69 1.54 1.46 0.74 Morpholine 2.33 1.96 Methylamine hydrochloride 0.1 Surfactant 0.004 Gum rosin powder 3 10 Isopropyl 90 Alcohol water Remaining Remaining Remaining Remaining Remaining Remaining Remaining

In the above table, the following hydrogenated rosin, polymerized rosin, gum rosin and surfactant were used. Hydrogenated rosin: (Arakawa Chemical Industry Co., Ltd .; KR-610) Polymerized rosin: (Arakawa Chemical Industry Co., Ltd .; Silvatac 2)
95) Gum rosin: (Arakawa Chemical Industries, Ltd .; U.S. gum rosin) Surfactant: Fluorocarbon nonionic surfactant

[0013]

[Table 2] Example Comparative example 1 2 3 4 5 6 1 2 Wettability of flux ○ ○ ○ ○ ○ ○ ～ ◎ × ◎ Spreading rate of solder 88.8 81.2 78.7 70.1 81.3 85.4 91.5 64.2 Corrosion None None None None None None None Appearance Uniform Uniform Uniform Uniform Uniform Uniform Separated Uniform

As is evident from the results shown in Table 2, the aqueous fluxes of the present invention of Examples 1 to 6 are not inferior in wettability and excellent in solder spreading rate as compared with conventional solvent-based fluxes. It can be seen that there is no corrosiveness and the appearance is uniform. In addition, the aqueous flux of the present invention is substantially free of an organic solvent, and is therefore friendly to the human body and the environment.

[0015]

As described in detail above, since the aqueous flux of the present invention containing rosin soap does not contain an organic solvent, it has no adverse effect on the human body and the environment, and has no corrosiveness and wetness. It has good properties and spread rate of solder.

Claims (3)

[Claims] An aqueous flux comprising a rosin soap. 2. The aqueous flux according to claim 1, which contains an organic acid, a halide or a halogenated organic acid salt. 3. The aqueous flux according to claim 1, further comprising a fungicide.